U.S. patent application number 12/248094 was filed with the patent office on 2009-05-21 for clutch mechanism.
This patent application is currently assigned to TOYOTA BOSHOKU KABUSHIKI KAISHA. Invention is credited to Atsuki SASAKI, Takao YAMAGUCHI.
Application Number | 20090126520 12/248094 |
Document ID | / |
Family ID | 40640569 |
Filed Date | 2009-05-21 |
United States Patent
Application |
20090126520 |
Kind Code |
A1 |
YAMAGUCHI; Takao ; et
al. |
May 21, 2009 |
CLUTCH MECHANISM
Abstract
A clutch mechanism for selectively transmitting a force applied
thereto may include an operation bracket that is rotatably
connected to the vehicle seat via a first pivot shaft and is
connected to a force output cable, a rotatable arm that is
rotatably connected to the operation bracket via the first pivot
shaft and is connected to a force input cable, and a swing arm that
is rotatably connected to the operation bracket via a second pivot
shaft. The operation bracket includes a curved slot formed therein.
The rotatable arm includes an elongated slot that has a toothed
portion. The swing arm includes an engagement portion that movably
engages both of the curved slot of the operation bracket and the
elongated slot of the rotatable arm.
Inventors: |
YAMAGUCHI; Takao;
(Toyota-shi, JP) ; SASAKI; Atsuki; (Nagoya-shi,
JP) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1950 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Assignee: |
TOYOTA BOSHOKU KABUSHIKI
KAISHA
Aichi-ken
JP
|
Family ID: |
40640569 |
Appl. No.: |
12/248094 |
Filed: |
October 9, 2008 |
Current U.S.
Class: |
74/89.38 ;
280/751 |
Current CPC
Class: |
Y10T 74/18696 20150115;
B60N 2/888 20180201 |
Class at
Publication: |
74/89.38 ;
280/751 |
International
Class: |
F16H 27/02 20060101
F16H027/02; B60R 21/055 20060101 B60R021/055 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 21, 2007 |
JP |
2007-301620 |
Claims
1. A clutch mechanism for selectively transmitting a force applied
thereto, comprising: an operation bracket that is rotatably
connected to the vehicle seat via a first pivot shaft and is
connected to a force output cable, the operation bracket including
a curved slot formed therein; a rotatable arm that is rotatably
connected to the operation bracket via the first pivot shaft and is
connected to a force input cable, the rotatable arm including an
elongated slot that has a toothed portion; and a swing arm that is
rotatably connected to the operation bracket via a second pivot
shaft, the swing arm including an engagement portion that movably
engages both of the curved slot of the operation bracket and the
elongated slot of the rotatable arm, wherein when the force is
applied quickly to the force input cable, the rotatable arm is
rotated quickly about the first pivot shaft relative to the
operation bracket whereas the swing arm is rotated slowly by a
gravitational force about the second pivot shaft along with
rotation of the rotatable arm, and as a result, the engagement
portion of the swing arm engages the toothed portion of the
elongated slot of the rotatable arm, wherein upon engagement of the
engagement portion of the swing arm and the toothed portion of the
rotatable arm, the rotatable arm can be rotationally locked with
respect to the operation bracket, so that the operation bracket is
rotated with the rotatable arm about the first pivot shaft, thereby
allowing transmission of the force to the force output cable,
wherein when the force is applied slowly to the force input cable,
the rotatable arm is rotated slowly about the first pivot shaft
relative to the operation bracket while the swing arm is rotated
slowly by the gravitational force about the second pivot shaft
along with rotation of the rotatable arm, and as a result, the
rotatable arm is continuously rotated relative to the operation
bracket while moving the engagement portion of the swing arm along
the elongated slot of the rotatable arm and the curved slot of the
operation bracket, and wherein upon continuous rotation of the
rotatable arm relative to the operation bracket, the operation
bracket can be prevented from being rotated about the first pivot
shaft, thereby inhibiting the transmission of the force to the
force output cable.
2. A force transmission mechanism for selectively transmitting a
force applied to a vehicle seat by a passenger that comprises: a
force input cable, a force output cable, a force receiving member
and a clutch mechanism, the force receiving member being arranged
and constructed to pull the force input cable when the force is
applied to the vehicle seat, the clutch mechanism including: an
operation bracket that is rotatably connected to the vehicle seat
via a first pivot shaft and is connected to the force output cable,
the operation bracket including a curved slot formed therein; a
rotatable arm that is rotatably connected to the operation bracket
via the first pivot shaft and is connected to the force input
cable, the rotatable arm including an elongated slot that has a
toothed portion; and a swing arm that is rotatably connected to the
operation bracket via a second pivot shaft, the swing arm including
an engagement portion that movably engages both of the curved slot
of the operation bracket and the elongated slot of the rotatable
arm, wherein when the force is applied quickly to the vehicle seat
such that the force input cable is quickly pulled, the rotatable
arm is rotated quickly about the first pivot shaft relative to the
operation bracket whereas the swing arm is rotated slowly by a
gravitational force about the second pivot shaft along with
rotation of the rotatable arm, and as a result, the engagement
portion of the swing arm engages the toothed portion of the
elongated slot of the rotatable arm, wherein upon engagement of the
engagement portion of the swing arm and the toothed portion of the
rotatable arm, the rotatable arm can be rotationally locked with
respect to the operation bracket, so that the operation bracket is
rotated with the rotatable arm about the first pivot shaft, thereby
allowing transmission of the force to the force output cable,
wherein when the force is applied slowly to the vehicle seat such
that the force input cable is slowly pulled, the rotatable arm is
rotated slowly about the first pivot shaft relative to the
operation bracket while the swing arm is rotated slowly by the
gravitational force about the second pivot shaft along with
rotation of the rotatable arm, and as a result, the rotatable arm
is continuously rotated relative to the operation bracket while
moving the engagement portion of the swing arm along the elongated
slot of the rotatable arm and the curved slot of the operation
bracket, and wherein upon continuous rotation of the rotatable arm
relative to the operation bracket, the operation bracket can be
prevented from being rotated about the first pivot shaft, thereby
inhibiting the transmission of the force to the force output
cable.
3. The force transmission mechanism as defined in claim 2, wherein
the force receiving member is rotatably attached to the vehicle
seat and is coupled to the force input cable, and wherein the force
receiving member is arranged and constructed to rotate so as to
pull the force input cable when the force is applied to the vehicle
seat.
4. The force transmission mechanism as defined in claim 2, wherein
the force output cable is associated with an active head rest
attached to the vehicle seat.
5. The force transmission mechanism as defined in claim 4, wherein
the head rest comprises a movable head rest main body that is
normally maintained in a retracted position via a lock mechanism,
and wherein the lock mechanism is arranged and constructed to be
unlocked when the force is transmitted to the force output cable
via the clutch mechanism, so that the head rest main body can be
moved to a projected position via a biasing member.
Description
[0001] This application claims priority to Japanese patent
application serial number 2007-301620, the contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to clutch mechanisms for use
in vehicle seats and force transmission mechanisms having such
clutch mechanisms. More particularly, the present invention relates
to clutch mechanisms that are constructed to function when external
forces are applied thereto via force input cables (e.g., when seat
backs of the seats are pressed rearwardly by backs of passengers
sitting on the vehicle seats), thereby selectively transmitting the
external forces to force output cables disposed in the seats as
pulling forces, and force transmission mechanisms having such
clutch mechanisms.
[0003] A clutch mechanism for use in a vehicle seat that is
constructed to function when an external force is applied thereto
is already known. Such a clutch mechanism is taught, for example,
by German Patent Number 10232017.
[0004] This clutch mechanism is constructed to function when an
external load or force is applied thereto (e.g., when a seat back
of the seat is pressed rearwardly by a back of a passenger sitting
on the seat), thereby transmitting the force to a lock mechanism of
a head rest. Upon transmission of the force to the lock mechanism,
the lock mechanism is changed to an unlocking condition, so that
the head rest can be tilted forwardly. Further, this clutch
mechanism is constructed to function only when the force is applied
quickly.
[0005] The known clutch mechanism is constructed to be
pneumatically actuated when the force is applied quickly thereto.
Therefore, the clutch mechanism may not properly function depending
on an ambient temperature even if the force is applied quickly. In
addition, the pneumatically actuated clutch mechanism may have a
complicated structure. This may lead to an increased manufacturing
cost of the clutch mechanism.
BRIEF SUMMARY OF THE INVENTION
[0006] In one aspect of the present invention, a clutch mechanism
for selectively transmitting a force applied thereto may include an
operation bracket that is rotatably connected to the vehicle seat
via a first pivot shaft and is connected to a force output cable, a
rotatable arm that is rotatably connected to the operation bracket
via the first pivot shaft and is connected to a force input cable,
and a swing arm that is rotatably connected to the operation
bracket via a second pivot shaft. The operation bracket includes a
curved slot formed therein. The rotatable arm includes an elongated
slot that has a toothed portion. The swing arm includes an
engagement portion that movably engages both of the curved slot of
the operation bracket and the elongated slot of the rotatable arm.
When the force is applied quickly to the force input cable, the
rotatable arm is rotated quickly about the first pivot shaft
relative to the operation bracket whereas the swing arm is rotated
slowly by a gravitational force about the second pivot shaft along
with rotation of the rotatable arm, and as a result, the engagement
portion of the swing arm engages the toothed portion of the
elongated slot of the rotatable arm. Upon engagement of the
engagement portion of the swing arm and the toothed portion of the
rotatable arm, the rotatable arm can be rotationally locked with
respect to the operation bracket, so that the operation bracket is
rotated with the rotatable arm about the first pivot shaft, thereby
allowing transmission of the force to the force output cable. When
the force is applied slowly to the force input cable, the rotatable
arm is rotated slowly about the first pivot shaft relative to the
operation bracket while the swing arm is rotated slowly by the
gravitational force about the second pivot shaft along with
rotation of the rotatable arm, and as a result, the rotatable arm
is continuously rotated relative to the operation bracket while
moving the engagement portion of the swing arm along the elongated
slot of the rotatable arm and the curved slot of the operation
bracket. Upon continuous rotation of the rotatable arm relative to
the operation bracket, the operation bracket can be prevented from
being rotated about the first pivot shaft, thereby inhibiting the
transmission of the force to the force output cable.
[0007] According to this aspect, when the force is applied quickly
to the force input cable, the rotatable arm can be reliably
rotationally locked with respect to the operation bracket (i.e.,
the rotatable arm can be mechanically integrated with the operation
bracket), so that the operation bracket can be reliably rotated
with the rotatable arm about the first pivot shaft. Therefore, when
the force is applied quickly to the force input cable, the force
can be reliably transmitted to the force output cable.
[0008] Also, because the swing arm is arranged and constructed to
be rotated by the gravitational force about the second pivot shaft,
it is not necessary to use springs or other such biasing members in
order to rotate the swing arm. Therefore, the clutch mechanism may
have a simplified structure. This may lead to an reduced
manufacturing cost of the clutch mechanism.
[0009] Other objects, features and advantages of the present
invention will be readily understood after reading the following
detailed description together with the accompanying drawings and
the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a perspective view of a vehicle seat having a lock
release mechanism (a clutch mechanism) according to a
representative embodiment of the present invention, in which
covering members of a seat back and a head rest are omitted;
[0011] FIG. 2 is a side view of the head rest, illustrating a
condition in which a head rest plate is in a normal position;
[0012] FIG. 3 is a side view of the head rest, illustrating a
condition in which the head rest plate is in a projected
position;
[0013] FIG. 4 is an exploded perspective view of the lock release
mechanism (the clutch mechanism);
[0014] FIG. 5 is an explanatory view illustrating motion of the
lock release mechanism (the clutch mechanism), which corresponds to
a condition in which a passenger does not sit on the seat;
[0015] FIG. 6 is an explanatory view illustrating the motion of the
lock release mechanism, which corresponds to an initial condition
after a force is applied quickly to the lock release mechanism via
a back of the passenger sitting on the seat;
[0016] FIG. 7 is an explanatory view illustrating the motion of the
clutch mechanism, which corresponds to a final condition after the
force is applied quickly to the lock release mechanism;
[0017] FIG. 8 is an explanatory view similar to FIG. 6, which
corresponds to an initial condition after the force is applied
slowly to the lock release mechanism; and
[0018] FIG. 9 is an explanatory view similar to FIG. 7, which
corresponds to a final condition after the force is applied slowly
to the lock release mechanism.
DETAILED DESCRIPTION OF THE INVENTION
[0019] A representative example of the present invention has been
described in detail with reference to the attached drawings. This
detailed description is merely intended to teach a person of skill
in the art further details for practicing preferred aspects of the
present invention and is not intended to limit the scope of the
invention. Only the claims define the scope of the claimed
invention. Therefore, combinations of features and steps disclosed
in the foregoing detail description may not be necessary to
practice the invention in the broadest sense, and are instead
taught merely to particularly describe detailed representative
examples of the invention. Moreover, the various features taught in
this specification may be combined in ways that are not
specifically enumerated in order to obtain additional useful
embodiments of the present invention.
[0020] A detailed representative embodiment of the present
invention is shown in FIG. 1 to FIG. 9.
[0021] As shown in FIG. 1, a representative vehicle seat 1 may
preferably include a seat cushion 10, a seat back 20 and a (active)
head rest 30. The seat back 20 may preferably include a back frame
F that is constituted of a pair of (right and left) vertical side
frame elements 21, a lateral upper frame element 22 and a lateral
lower plate-shaped frame element 21a. Lower end portions of the
side frame elements 21 are respectively rotatably connected to
reclining plates 11 of the seat cushion 10 via seat reclining
devices R (one of which is shown), so that a tilting angle of the
seat back 20 (the back frame F) relative to the seat cushion 10 can
be adjusted by operating the seat reclining devices R. Naturally,
the seat back 20 includes a cushion member and a covering member
attached to the back frame F, which members are omitted in FIGS. 1
to 4 for clarity.
[0022] As shown in FIG. 1, the head rest 30 may preferably include
a base element 31 and a head rest plate (a head rest main body) 33.
The head rest plate 33 is movably connected to the base element 31
via a special linking mechanism. Also, the head rest 30 may include
a pair of stays 32 that are integrally connected to the base
element 31. The stays 32 are connected to the upper frame element
22 of the back frame F via a pair of attachment members 22a
attached to the upper frame element 22. As will be appreciated, the
attachment members 22a are respectively provided with retainers 23
that are capable of retaining the stays 32. Further, the head rest
30 includes a cushion member and a covering member attached to the
head rest main body, which members are omitted in FIGS. 1 to 4 for
clarity.
[0023] As shown in FIGS. 2 and 3, the linking mechanism is composed
of a rigid arm 34, a movable linking arm 35, and an elongated slot
36 formed in the base element 31. The rigid arm 34 is fixedly
connected to the head rest plate 33 so as to be projected
rearwardly. A rearwardly projected end of the rigid arm 34 may
preferably movably engage the slot 36 via a slide pin 34a so as to
move or slide therealong. The linking arm 35 is pivotally connected
to the head rest plate 33 via a pivot pin 35a. Also, the linking
arm 35 is pivotally connected to the base element 31 via a pivot
pin 35b. Thus, the head rest plate 33 is capable of moving between
a retracted position (FIG. 2) and a projected position (FIG. 3)
when the linking arm 35 is rotated about the pivot pin 35b.
Further, the linking arm 35 is biased clockwise about the pivot pin
35b via a biasing member (not shown) such that the head rest plate
33 can be projected to the projected position. However, the linking
arm 35 is normally rotated counterclockwise against a biasing force
of the biasing member via a lock mechanism (not shown) of the head
rest 30 (the head rest plate 33), so that the head rest plate 33
can be normally moved to and maintained in the retracted position.
As will be recognized, when the lock mechanism is released or
unlocked, the linking arm 35 can be rotated clockwise by the
biasing force of the biasing member, so that the head rest plate 33
can be moved to the projected position from the retracted
position.
[0024] The lock mechanism of the head rest 30 is associated to a
lock release mechanism (a force transmission mechanism) that is
attached to the seat back 20. As shown in, for example, FIGS. 4 and
5, the lock release mechanism may preferably include a clutch
mechanism 40, a force receiving member 41, a first force
transmission cable (a force output cable) 60 that is positioned
between the clutch mechanism 40 and the lock mechanism, and a
second force transmission cable (a force input cable) 70 that is
positioned between the clutch mechanism 40 and the force receiving
member 41.
[0025] As best shown in FIG. 4, the clutch mechanism 40 may
preferably include a plate-shaped base member 25, a plate-shaped
rotatable bracket (an operation bracket) 45, an elongated
plate-shaped rotatable arm 46, and an elongated plate-shaped swing
arm 48.
[0026] The base member 25 is fixedly connected to an inner surface
of either one of the side frame elements 21 (the right-hand side
frame element 21 in this embodiment) via a pair of connector pins
26. The base member 25 has a transversely projected hook portion
25a.
[0027] The rotatable bracket 45 has substantially a pentagonal
shape. The rotatable bracket 45 is rotatably connected to the base
member 25 via a transversely directed pivot pin (a first pivot
shaft) 42 at a corner portion thereof. Further, the rotatable
bracket 45 has an elongated curved slot 45a (which will be
hereinafter described). The rotatable bracket 45 thus formed is
connected to the first force transmission cable 60 (which will be
hereinafter described).
[0028] The rotatable arm 46 has substantially a rectangular shape.
The rotatable arm 46 is rotatably connected to the base member 25
via the pivot pin 42 at one end portion thereof while the rotatable
bracket 45 is interleaved therebetween. That is, the rotatable arm
46 is positioned to be laterally adjacent to the rotatable bracket
45 and is rotatably connected to the base member 25 via the pivot
pin 42 (a common pivot pin). Further, the rotatable arm 46 is
arranged so as to freely rotate relative to the rotatable bracket
45. The rotatable arm 46 has an elongated toothed slot 47 that is
longitudinally formed therein. In particular, as best shown in FIG.
4, the toothed slot 47 has a non-toothed flattened longitudinal
wall (a non-toothed portion) 47a (which correspond to a lower wall
in this embodiment) and a toothed longitudinal wall (a toothed
portion) 47b (which correspond to an upper wall in this
embodiment). The rotatable arm 46 thus formed is connected to the
second force transmission cable 70 (which will be hereinafter
described) at the other end portion thereof.
[0029] The swing arm 48 is rotatably connected to the rotatable
bracket 45 via a transversely directed pivot pin (a second pivot
shaft) 50 at one end portion thereof. Further, the swing arm 48 may
preferably connected to a corner portion of the rotatable bracket
45, which corner portion is positioned adjacent to the corner
portion corresponding to the pivot pin 42. The swing arm 48 has an
engagement projection (an engagement portion) 48a that is
positioned at the other end portion thereof. The engagement
projection 48a is laterally inwardly projected so as to slidably
engage the curved slot 45a of the rotatable bracket 45 through the
toothed slot 47 of the rotatable arm 46.
[0030] Further, the curved slot 45a of the rotatable bracket 45 may
preferably have a circular arc shape centered on the pivot pin 50
and having a radius of curvature equal to a distance between the
pivot pin 50 and the engagement projection 48a. Therefore, when the
rotatable arm 46 is rotated about the pivot pin 42, the swing arm
48 can be smoothly rotated in the same direction about the pivot
pin 50 while the engagement projection 48a moves along the toothed
slot 47 of the rotatable arm 46 and the curved slot 45a of the
rotatable bracket 45.
[0031] As best shown in FIG. 4, the force receiving member 41 is
composed of a curved plate having a force receiving portion 41a and
an outer cable attachment portion 41b. The force receiving member
41 is rotatably connected to a pair of attachment brackets 21b
formed in the lower frame element 21a of the back frame F via a
pair of transversely directed pivot pins 43, so as to be vertically
rearwardly rotated about the pivot pins 43 when the force receiving
portion 41a is pressed rearwardly by a back of a passenger sitting
on the vehicle seat 1.
[0032] Further, at least one of the pivot pins 43 is provided with
a torsion spring (not shown) of which the both ends respectively
engage the force receiving member 41 and the lower frame element
21a, so that the force receiving member 41 can normally be biased
vertically forwardly (i.e., counterclockwise in FIG. 5) about the
pivot pins 43. That is, as shown in FIG. 5, the force receiving
portion 41a of the force receiving member 41 may preferably
normally contact an inner surface of the cushion member (which is
shown by a reference sign P) of the seat back 20.
[0033] As will be appreciated, when the cushion member P of the
seat back 20 is pressed rearwardly by the back of the passenger
sitting on the vehicle seat 1, the force receiving portion 41a of
the force receiving member 41 is correspondingly pressed
rearwardly. As a result, the force receiving member 41 is
vertically rearwardly (i.e., clockwise in FIG. 5) rotated about the
pivot pins 43 against a spring force of the torsion spring.
[0034] Further, the torsion spring may simply function to contact
the force receiving member 41 with the cushion member P of the seat
back 20. Therefore, the torsion spring may preferably have a
(small) force that is sufficient to contact the force receiving
member 41 with the cushion member P.
[0035] As shown in FIGS. 1 and 4, the first force transmission
cable 60 is composed of a flexible tubular outer member (sheath)
61, and an inner member (wire) 62 that is inserted into the outer
member 61. As shown in FIG. 1, an upper end of the outer member 61
is attached to one of the stays 32 of the head rest 30. Conversely,
a lower end of the outer member 61 is attached to the hook portion
25a of the base member 25. Further, an upper end of the inner
member 62 is introduced into one of the stays 32 of the head rest
30 and is coupled to the lock mechanism of the head rest 30.
Conversely, as best shown in FIG. 4, a lower end of the inner
member 62 is attached to the rotatable bracket 45 via a connector
pin 63. Further, the connector pin 63 may preferably be positioned
at substantially a corner portion of the rotatable bracket 45,
which corner portion is positioned diagonally opposite to the
corner portion corresponding to the pivot pin 50.
[0036] Thus, when the rotatable bracket 45 is rotated forwardly
(counterclockwise in FIG. 5), the inner member 62 of the first
force transmission cable 60 is pulled, so that the lock mechanism
of the head rest 30 can be unlocked. As a result, the head rest
plate 33 can be projected to the projected position from the
retracted position.
[0037] As shown in FIGS. 1 and 4, the second force transmission
cable 70 is composed of a flexible tubular outer member (sheath)
71, and an inner member (wire) 72 that is inserted into the outer
member 71. An upper end of the outer member 71 is attached to an
attachment bracket 24 that is fixedly attached to the right-hand
side frame element 21. Conversely, a lower end of the outer member
71 is attached to the outer cable attachment portion 41b of the
force receiving member 41. Further, an upper end of the inner
member 72 is connected to the other end portion (free end portion)
of the rotatable arm 46 via a connector pin 73. Conversely, as best
shown in FIG. 4, a lower end of the inner member 72 is attached to
an attachment portion 21c that is formed in the lower frame element
21a.
[0038] Thus, when the force receiving member 41 is vertically
rearwardly (clockwise in FIG. 5) rotated about the pivot pins 43,
the inner member 72 of the second force transmission cable 70 is
pulled, so that the rotatable arm 46 can be rotated forwardly
(counterclockwise in FIG. 5) about the pivot pin 42.
[0039] Further, in a (normal) condition in which a passenger does
not sit on the seat and in which a load or force is not applied to
the cushion member P of the seat back 20 (i.e., the force receiving
portion 41a of the force receiving member 41 is not pressed
rearwardly), the rotatable bracket 45, the rotatable arm 46 and the
swing arm 48 are respectively positioned at uppermost angular
positions (FIG. 5). Further, as shown in FIG. 5, the curved slot
45a of the rotatable bracket 45 may preferably be formed such that
the engagement projection 48a of the swing arm 48 can be positioned
at substantially an uppermost end of the curved slot 45a when the
rotatable bracket 45, the rotatable arm 46 and the swing arm 48 are
positioned at these angular positions. Similarly, the toothed slot
47 of the rotatable arm 46 may preferably be formed such that the
engagement projection 48a of the swing arm 48 can be positioned at
substantially a proximal end of the toothed slot 47 when the
rotatable bracket 45, the rotatable arm 46 and the swing arm 48 are
positioned at these angular positions.
[0040] Next, an operation of the lock release mechanism (in
particular, the clutch mechanism 40) thus constructed will be
described.
[0041] In the condition shown in FIG. 5, when the force is applied
quickly to the cushion member P of the seat back 20 by the back of
the passenger sitting on the vehicle seat 1 (for example, when a
back-side collision of a vehicle happens), the force receiving
portion 41a of the force receiving member 41 is quickly pressed
rearwardly. As a result, as shown in FIG. 6, the force receiving
member 41 is vertically rearwardly (clockwise) rotated about the
pivot pins 43 against the spring force of the torsion spring (not
shown). Upon rotation of the force receiving member 41, as
previously described, the inner member 72 of the second force
transmission cable 70 is pulled downwardly, so that the rotatable
arm 46 can be rotated forwardly (counterclockwise) about the pivot
pin 42. At the same time, the swing arm 48 can be rotated forwardly
(counterclockwise) by a gravitational force about the pivot pin 50
along with rotation of the rotatable arm 46 while the engagement
projection 48a moves along the toothed slot 47 of the rotatable arm
46 and the curved slot 45a of the rotatable bracket 45.
[0042] At this time, the rotatable arm 46 can be rotated quickly
because the force is applied quickly to the cushion member P (the
force receiving member 41) whereas the swing arm 48 is rotated
slowly because it is rotated only by the gravitational force. That
is, the rotatable arm 46 can be rotated faster than the swing arm
48. As a result, as shown in FIG. 6, the engagement projection 48a
of the swing arm 48 can engage the toothed wall 47b of the toothed
slot 47 immediately after the rotatable arm 46 starts to rotate. At
this time, the engagement projection 48a can be pressed to an
inside surface 45b of the curved slot 45a of the rotatable bracket
45. Thus, the rotatable arm 46 can be effectively prevented from
rotating forwardly relative to the rotatable bracket 45. As a
result, the rotatable arm 46 can be rotationally locked with
respect to the rotatable bracket 45. That is, the rotatable arm 46
can be mechanically integrated with the rotatable bracket 45.
[0043] When the force receiving portion 41a of the force receiving
member 41 is further (quickly) pressed rearwardly after the
engagement projection 48a of the swing arm 48 engages the toothed
wall 47b of the toothed slot 47 (i.e., after the rotatable arm 46
is rotationally locked with respect to the rotatable bracket 45),
as shown in FIG. 7, the rotatable bracket 45 can be rotated
forwardly (counterclockwise) with the rotatable arm 46 about the
pivot pin 42.
[0044] Upon counterclockwise rotation of the rotatable bracket 45,
as previously described, the inner member 62 of the first force
transmission cable 60 is pulled downwardly (i.e., the force is
transmitted to the force output cable), so that the lock mechanism
of the head rest 30 can be unlocked. As a result, the head rest
plate 33 of the head rest 30 can be moved to the projected position
from the retracted position.
[0045] Thus, if the back-side collision of the vehicle happens, the
head rest main body (the head rest plate 33) moves closer to a head
of the passenger, so that the head of the passenger can be quickly
and reliably supported by the head rest main body. Therefore, the
passenger can be prevented from suffering an injury, such as
whiplash.
[0046] Conversely, when the force is applied slowly to the cushion
member P of the seat back 20 by the back of the passenger (for
example, when the passenger normally gets in and out the vehicle
seat 1), the force receiving portion 41a of the force receiving
member 41 is slowly pressed rearwardly. As a result, as shown in
FIG. 8, the force receiving member 41 is vertically rearwardly
(clockwise) rotated about the pivot pins 43 against a spring force
of the torsion spring (not shown). Upon rotation of the force
receiving member 41, the inner member 72 of the second force
transmission cable 70 is pulled downwardly, so that the rotatable
arm 46 can be rotated forwardly (counterclockwise) about the pivot
pin 42. At the same time, the swing arm 48 can be rotated forwardly
(counterclockwise) by the gravitational force about the pivot pin
50 while the engagement projection 48a moves along the toothed slot
47 of the rotatable arm 46 and the curved slot 45a of the rotatable
bracket 45.
[0047] At this time, the rotatable arm 46 can be rotated slowly
because the force is applied slowly to the cushion member P (the
force receiving member 41) while the swing arm 48 is rotated slowly
because it is rotated only by the gravitational force. That is, the
rotatable arm 46 can be rotated at substantially the same speed as
the swing arm 48. As a result, as shown in FIG. 8, the engagement
projection 48a of the swing arm 48 cannot engage the toothed wall
47b of the toothed slot 47. In other words, the engagement
projection 48a of the swing arm 48 can freely move along the
non-toothed wall 47a of the toothed slot 47. Thus, the rotatable
arm 46 can be rotated about the pivot pin 42 while rotating the
swing arm 48 about the pivot pin 50. That is, the rotatable arm 46
can be rotated without interfering with the swing arm 48 (the
engagement projection 48a). As a result, the rotatable arm 46 can
continuously rotate forwardly relative to the rotatable bracket 45.
In other words, the rotatable arm 46 cannot be rotationally locked
with respect to the rotatable bracket 45.
[0048] When the force receiving portion 41a of the force receiving
member 41 is further (slowly) pressed rearwardly, as shown in FIG.
9, the rotatable arm 46 can be further rotated about the pivot pin
42 while rotating the swing arm 48 about the pivot pin 50 until the
engagement projection 48a of the swing arm 48 reaches a proximal
end of the toothed slot 47 of the rotatable arm 46. At this time,
the rotatable bracket 45 cannot be rotated forwardly
(counterclockwise) because the rotatable arm 46 is not rotationally
locked with respect to the rotatable bracket 45.
[0049] As described above, when the force is applied slowly to the
cushion member P of the seat back 20, the rotatable bracket 45
cannot be rotated with the rotatable arm 46. Therefore, the inner
member 62 of the first force transmission cable 60 is not pulled
(i.e., the force is not transmitted to the force output cable), so
that the lock mechanism of the head rest 30 cannot be unlocked. As
a result, the head rest plate 33 of the head rest 30 can be
maintained in the retracted position.
[0050] Thus, even if the force is applied to the cushion member P
of the seat back 20 due to normal movements of the passenger, the
head rest plate 33 of the head rest 30 cannot be projected.
Therefore, the passenger can normally be prevented from suffering
discomfort.
[0051] According to the lock release mechanism of the present
embodiment, the force that is applied quickly to the cushion member
P of the seat back 20 can be reliably transmitted to the rotatable
bracket 45 of the clutch mechanism 40 without being influenced by
an ambient temperature. Therefore, when the force is applied
quickly to the cushion member P of the seat back 20, the clutch
mechanism 40 may properly function regardless of the ambient
temperature. As a result, the force can be reliably transmitted to
the lock mechanism of the head rest 30, so as to unlock the lock
mechanism of the head rest 30. Thus, if the back-side collision of
the vehicle happens, the head rest plate 33 of the head rest 30 can
be projected to the projected position from the retracted position,
so that the head of the passenger can be quickly and reliably
supported thereby.
[0052] In addition, because the swing arm 48 is arranged and
constructed to be rotated forwardly (counterclockwise) by the
gravitational force about the pivot pin 50, it is not necessary to
use springs or other such biasing members. Therefore, the clutch
mechanism 40 may have a simplified structure. This may lead to an
reduced manufacturing cost of the clutch mechanism 40 (the lock
release mechanism).
[0053] Naturally, various changes and modifications may be made to
the present invention without departing from the scope of the
invention. For example, sizes and shapes of the rotatable bracket
45 (the curved slot 45a) and the rotatable arm 46 (the toothed slot
47) can be changed in consideration of a body type and a body size
of the passenger, if necessary.
[0054] Further, in this embodiment, the force receiving portion 41a
of the force receiving member 41 is pressed to the inner surface of
the cushion member P of the seat back 20 by the spring force of the
torsion spring. However, the force receiving portion 41a of the
force receiving member 41 can be connected or bonded to the inner
surface of the cushion member P of the seat back 20, if
necessary.
* * * * *